This invention relates to a cleaning device for removing an untransferred toner remaining on the circumferential surface of a photoconductor drum, and more specifically, to a cleaning device disposed above the photoconductor drum, and an image forming apparatus equipped with the cleaning device.
In recent years, there have been increases in electrostatic copiers of an in-body paper delivery type in which a paper stack space is provided in a region between image forming means, including a photoconductor drum, and document exposure/image reading means disposed above the image forming means in the body of an image forming apparatus to achieve compactness of the entire apparatus. In such a copier, paper is transported vertically upwardly from a paper feed cassette or a manual paper feed tray disposed below the image forming means. While the paper transported vertically upwardly is passing through a transfer zone disposed beside the photoconductor drum, a toner is transferred to the paper by transfer means. The paper having the toner transferred thereto is transported, unchanged, vertically upwardly, and then passed beside a fixing device. During this passage, the toner transferred to the paper is fixed onto the paper. The paper bearing the fixed toner is transported vertically upwardly, then changed in the direction of transport, and transported in a horizontal direction. Finally, the paper is delivered to a paper receiving tray in the paper stack space. The untransferred toner, which has not been transferred onto the paper, but has remained on the circumferential surface of the photoconductor drum, is removed by a cleaning device provided downstream from the transfer zone in the direction of rotation of the photoconductor drum. In such a copier of the in-body paper delivery type, the paper is transported vertically upwardly beside the photoconductor drum. Thus, there is no choice but to provide the cleaning device above the photoconductor drum. As a result, the cleaning device is configured to have a lower end portion downwardly opening toward the circumferential surface of the photoconductor drum.
Of the copiers of the in-body paper delivery type, those operating at a low speed have been predominant conventionally, but have recently been replaced by high speed ones gradually. With this technical background, the copiers in the above-mentioned configuration are increasing the use of a low temperature fixing toner, an a-Si(amorphous silicon)-based photoconductor drum, or a high sensitivity OPC (Organic Photoconductor) photoconductor drum.
When the toner remaining on the circumferential surface of the photoconductor drum is removed using a cleaning blade, additives detached from the toner may deposit on the circumferential surface of the photoconductor drum, and may be unremovable by cleaning. If the additives remain on the circumferential surface of the photoconductor drum, the remaining additives form cores, around which the poorly cleanable toner grows, forming masses. Every time the resulting masses slip beside the cleaning blade, they fuse, leaving streaky toner deposits on the circumferential surface of the photoconductor drum. Since a fresh toner is developed on the toner deposits, copy smudges resembling black spots corresponding to the toner deposits appear on the surface of the paper which is a copy. Particularly when the low temperature fixing toner is used, this tendency is marked. With the speeding of the in-body paper delivery type copier, a demand is becoming intense for a solution to this problem. Furthermore, when a magnetic toner is used, the following facts are presented: First, a magnetic powder contained in the magnetic toner, such as magnetite, becomes a causative substance, like the aforementioned detached additives, for the toner deposits on the circumferential surface of the photoconductor drum. Secondly, if a high copying speed is intended, a binder resin needs to have the property of fixing at an even lower temperature, in order to obtain fixing performance comparable to that of a nonmagnetic toner with the use of the magnetic toner. For these reasons, black spot-like copy smudges may occur noticeably. Even in light of the difference in weight between the magnetic toner and the nonmagnetic toner, if the copying speed of the in-body paper delivery type copier is increased, black spot-like smudges of the copy due to the deposition of the toner is even more marked, posing a problem to be solved.
Furthermore, the photoconductor drum itself poses the following problem: When an a-Si-based photoconductor drum is used, products of electric discharge, such as NOx and SOx, are generated by a main charger, a transfer charger, and a static eliminator disposed around the photoconductor drum. When these discharge products are exposed to a high humidity environment while depositing on the circumferential surface of the photoconductor drum, they adsorb moisture in the air to disturb an electrostatic latent image on the circumferential surface of the photoconductor drum, thereby causing image distortion. In addition, ozone which develops from the chargers and the static eliminator oxidizes and deteriorates the circumferential surface of the photoconductor drum, causing a tendency toward aggravation of image distortion. If a photoconductor drum other than the a-Si-based photoconductor drum, for example, the OPC photoconductor drum, is used, on the other hand, the toner undergoes filming on the circumferential surface of the photoconductor drum. As a result, photosensitivity and chargeability decline, so that fog in non-image areas or a decrease in image density tends to occur. Filming of the toner refers to the phenomenon that during repeated image formation and cleaning for long periods of time, the toner particles pressed against, slid over and rubbed against the circumferential surface of the photoconductor drum by the cleaning blade are deformed plastically and fused in a film form onto the circumferential surface.
To deal with the foregoing problems, it is necessary to polish the circumferential surface of the photoconductor drum aggressively, and always maintain the circumferential surface of the photoconductor drum in a clean state. For this purpose, a cleaning roller composed of an elastic material such as urethane rubber is provided upstream from the cleaning blade. This cleaning roller is driven so as to be rotationally moved in the same direction as the photoconductor drum at a peripheral speed higher than that of the photoconductor drum at the site of its pressurized contact with the photoconductor drum. Alternatively, the cleaning roller is rotated in a manner following the photoconductor drum. By so doing, the cleaning roller is slid over and rubbed against the circumferential surface of the photoconductor drum to polish it. More concretely, the cleaning roller shows its own action of cleaning, and in addition, polishes the circumferential surface of the photoconductor drum by sliding on and rubbing against it via the toner and the toner additives remaining on the circumferential surface of the photoconductor drum, thereby keeping the circumferential surface of the photoconductor drum always clean. Consequently, image distortion, toner filming, or toner deposition on the circumferential surface of the photoconductor drum is prevented.
As described above, it is desirable in the in-body paper delivery type copier to provide the cleaning roller in the cleaning device. However, the provision of the cleaning roller in addition to the cleaning blade and the toner outletting spiral means requires a considerable proportion of the space around the photoconductor drum, inducing upsizing of the entire copier. An alternative measure would be to thrust the cleaning blade in the axial direction of the photoconductor drum, thereby minimizing the slipping escape of the deposited toner from the cleaning blade. Even if this measure is taken, however, image distortion and toner filming cannot be prevented effectively, and seal between the cleaning blade and the circumferential surface of the photoconductor drum is decreased, whereupon the toner falls toward the photoconductor drum, causing the risks of copy smudges and dirt inside the apparatus. Besides, because of the thrust of the cleaning blade, the edge face of the cleaning blade is liable to damage, disadvantaging the long life of the apparatus.
A further problem with the prior art exists. That is, when an ordinary cleaning device is disposed, unchanged, above the photoconductor drum, the toner outletting spiral means is provided upstream from the cleaning blade in the direction of rotation of the photoconductor drum. Thus, the toner recovered is rendered stagnant above the cleaning blade by the transport action of the photoconductor drum itself, whereby the toner transport ability of the toner outletting spiral means fails to work effectively. As a result, toner agglomeration, toner blocking or the like occurs, so that the action of outletting the recovered toner is itself insufficient. In the worst case, there may be a serious trouble, such as the toner outletting spiral means becoming locked.
An object of the present invention is to provide a novel cleaning device, which accommodates a cleaning blade, a cleaning roller and toner outletting spiral means compactly and which can downsize the entire structure, and more specifically, a novel cleaning device disposed above a photoconductor drum for removing an untransferred toner remaining on the circumferential surface of the photoconductor drum; and a novel image forming apparatus equipped with the cleaning device.
Another object of the present invention is to provide a novel cleaning device which prevents the occurrence of toner agglomeration or toner blocking until the recovered toner is let out, and which enables the recovered toner to be transported and let out smoothly and promptly, and more specifically, a novel cleaning device disposed above the photoconductor drum for removing an untransferred toner remaining on the circumferential surface of the photoconductor drum; and a novel image forming apparatus equipped with the cleaning device.
Yet another object of the present invention is to provide a novel cleaning device which enables the recovered toner to be promptly transported toward the outside and let out without being leaked to the outside, and more specifically, a novel cleaning device disposed above the photoconductor drum for removing an untransferred toner remaining on the circumferential surface of the photoconductor drum; and a novel image forming apparatus equipped with the cleaning device.
A further object of the present invention is to provide a novel image forming apparatus of an in-body paper delivery type which ensures satisfactory image formation and which permits a high copying speed.
A still further object of the present invention is to provide a novel image forming apparatus of an in-body paper delivery type which prevents image distortion, toner filming and toner deposition occurring on the circumferential surface of the photoconductor drum, and which enables a maintenance cycle to be extended.
According to an aspect of the present invention, there is provided a cleaning device comprising:
a housing disposed above a photoconductor drum and having an opening portion open downward toward a circumferential surface of the photoconductor drum;
a cleaning blade disposed in the housing so as to be located in the opening portion downstream in a direction of rotation of the photoconductor drum; and
a cleaning roller disposed in the housing so as to be located in the opening portion upstream from the cleaning blade in the direction of rotation of the photoconductor drum, and wherein, in the housing,
toner outletting spiral means for letting out a toner recovered into the housing is disposed above the cleaning blade;
a partition wall is disposed between the cleaning blade and the toner outletting spiral means; and
a toner movement space for moving the toner recovered into the housing is formed between a front end of the partition wall and a circumferential surface of the cleaning roller.
Preferably, when a rotation region of the toner outletting spiral means is viewed in a vertical direction, the partition wall extends out from a downstream end of the rotation region toward an upstream end of the rotation region in the direction of rotation of the photoconductor drum; and when the rotation region is viewed in the vertical direction, an effective length of shielding of the rotation region by the partition wall is 30% or more of a diameter of the rotation region.
Preferably, the front end of the partition wall is disposed nearly vertically below a center of rotation of the toner outletting spiral means.
Preferably, the horizontal distance at which the front end of the partition wall and the circumferential surface of the cleaning roller maximally approach each other is 2 mm or more.
Preferably, the circumferential surface of the cleaning roller rotationally moves in the same direction as the circumferential surface of the photoconductor drum at a site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum; a scraper is disposed within the housing; and a front end portion of the scraper is brought into pressurized contact with the circumferential surface of the cleaning roller at a position downstream from the site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum in a direction of rotation of the cleaning roller, with a front end of the scraper being directed in a direction opposite to the direction of rotation of the cleaning roller.
Preferably, the scraper is disposed so as to be capable of scraping off the toner deposited on the circumferential surface of the cleaning roller either to a gap between the cleaning roller and the toner outletting spiral means, or toward a rotation region of the toner outletting spiral means.
Preferably, the distance at which the circumferential surface of the cleaning roller and a rotation region of the toner outletting spiral means maximally approach each other is 3 mm or less.
Preferably, the cleaning roller functions as a polishing roller, because the circumferential surface of the cleaning roller makes pressurized contact with the circumferential surface of the photoconductor drum via the toner.
According to another aspect of the present invention, there is provided a cleaning device comprising:
a housing disposed above a photoconductor drum and having an opening portion open downward toward a circumferential surface of the photoconductor drum;
a cleaning blade disposed in the housing so as to be located in the opening portion downstream in a direction of rotation of the photoconductor drum; and
a cleaning roller disposed in the housing so as to be located in the opening portion upstream from the cleaning blade in the direction of rotation of the photoconductor drum, and wherein
toner outletting spiral means for letting out a toner recovered into the housing is disposed above the cleaning blade in the housing;
a scraper is disposed within the housing;
a circumferential surface of the cleaning roller rotationally moves in the same direction as the circumferential surface of the photoconductor drum at a site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum;
a front end portion of the scraper is brought into pressurized contact with the circumferential surface of the cleaning roller at a position downstream from the site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum in a direction of rotation of the cleaning roller, with a front end of the scraper being directed in a direction opposite to the direction of rotation of the cleaning roller; and
the scraper is disposed so as to be capable of scraping off the toner deposited on the circumferential surface of the cleaning roller either to a gap between the cleaning roller and the toner outletting spiral means, or toward a rotation region of the toner outletting spiral means.
Preferably, in the housing, a partition wall is disposed between the cleaning blade and the toner outletting spiral means; and a toner movement space for moving the toner recovered into the housing is formed between a front end of the partition wall and the circumferential surface of the cleaning roller.
Preferably, the cleaning roller functions as a polishing roller, because the circumferential surface of the cleaning roller makes pressurized contact with the circumferential surface of the photoconductor drum via the toner.
According to still another aspect of the present invention, there is provided an image forming apparatus comprising:
a photoconductor drum; and
a cleaning device for removing a toner remaining on a circumferential surface of the photoconductor drum,
the cleaning device comprising:
a housing disposed above a photoconductor drum and having an opening portion open downward toward the circumferential surface of the photoconductor drum;
a cleaning blade disposed in the housing so as to be located in the opening portion downstream in a direction of rotation of the photoconductor drum; and
a cleaning roller disposed in the housing so as to be located in the opening portion upstream from the cleaning blade in the direction of rotation of the photoconductor drum, and wherein, in the housing,
toner outletting spiral means for letting out the toner recovered into the housing is disposed above the cleaning blade;
a partition wall is disposed between the cleaning blade and the toner outletting spiral means; and
a toner movement space for moving the toner recovered into the housing is formed between a front end of the partition wall and a circumferential surface of the cleaning roller.
Preferably, when a rotation region of the toner outletting spiral means is viewed in a vertical direction, the partition wall extends out from a downstream end of the rotation region toward an upstream end of the rotation region in the direction of rotation of the photoconductor drum; and when the rotation region is viewed in the vertical direction, an effective length of shielding of the rotation region by the partition wall is 30% or more of a diameter of the rotation region.
Preferably, the front end of the partition wall is disposed nearly vertically below a center of rotation of the toner outletting spiral means.
Preferably, the horizontal distance at which the front end of the partition wall and the circumferential surface of the cleaning roller maximally approach each other is 2 mm or more.
Preferably, the circumferential surface of the cleaning roller rotationally moves in the same direction as the circumferential surface of the photoconductor drum at a site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum; a scraper is disposed within the housing; and a front end portion of the scraper is brought into pressurized contact with the circumferential surface of the cleaning roller at a position downstream from the site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum in a direction of rotation of the cleaning roller, with a front end of the scraper being directed in a direction opposite to the direction of rotation of the cleaning roller.
Preferably, the scraper is disposed so as to be capable of scraping off the toner deposited on the circumferential surface of the cleaning roller either to a gap between the cleaning roller and the toner outletting spiral means, or toward a rotation region of the toner outletting spiral means.
Preferably, the distance at which the circumferential surface of the cleaning roller and a rotation region of the toner outletting spiral means maximally approach each other is 3 mm or less.
Preferably, the cleaning roller functions as a polishing roller, because the circumferential surface of the cleaning roller makes pressurized contact with the circumferential surface of the photoconductor drum via the toner.
Preferably, the image forming apparatus comprises an image forming apparatus body; image forming means disposed in the body and including the photoconductor drum and the cleaning device; document exposure/image reading means disposed within an upper end portion of the body and above the image forming means; a paper stack space portion disposed in a region between the image forming means and the document exposure/image reading means in the body; and a paper transport passage extending in a vertical direction beside the photoconductor drum and adapted to guide fed paper to the paper stack space portion.
Preferably, the photoconductor drum comprises an a-Si-based photoconductor drum, and the peripheral speed of the cleaning roller is greater than the peripheral speed of the photoconductor drum.
Preferably, the toner comprises a magnetic toner.
According to a further aspect of the present invention, there is provided an image forming apparatus comprising:
a photoconductor drum; and
a cleaning device for removing a toner remaining on a circumferential surface of the photoconductor drum,
the cleaning device comprising:
a housing disposed above the photoconductor drum and having an opening portion open downward toward the circumferential surface of the photoconductor drum;
a cleaning blade disposed in the housing so as to be located in the opening portion downstream in a direction of rotation of the photoconductor drum; and
a cleaning roller disposed in the housing so as to be located in the opening portion upstream from the cleaning blade in the direction of rotation of the photoconductor drum, and wherein
toner outletting spiral means for letting out the toner recovered into the housing is disposed above the cleaning blade in the housing;
a scraper is disposed within the housing;
a circumferential surface of the cleaning roller rotationally moves in the same direction as the circumferential surface of the photoconductor drum at a site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum;
a front end portion of the scraper is brought into pressurized contact with the circumferential surface of the cleaning roller at a position downstream from the site of pressurized contact between the circumferential surface of the cleaning roller and the circumferential surface of the photoconductor drum in a direction of rotation of the cleaning roller, with a front end of the scraper being directed in a direction opposite to the direction of rotation of the cleaning roller; and
the scraper is disposed so as to be capable of scraping off the toner deposited on the circumferential surface of the cleaning roller either to a gap between the cleaning roller and the toner outletting spiral means, or toward a rotation region of the toner outletting spiral means.
Preferably, in the housing, a partition wall is disposed between the cleaning blade and the toner outletting spiral means; and a toner movement space for moving the toner recovered into the housing is formed between a front end of the partition wall and the circumferential surface of the cleaning roller.
Preferably, the cleaning roller functions as a polishing roller, because the circumferential surface of the cleaning roller makes pressurized contact with the circumferential surface of the photoconductor drum via the toner.
Preferably, the image forming apparatus comprises: an image forming apparatus body; image forming means disposed in the body and including the photoconductor drum and the cleaning device; document exposure/image reading means disposed within an upper end portion of the body and above the image forming means; a paper stack space portion disposed in a region between the image forming means and the document exposure/image reading means in the body; and a paper transport passage extending in a vertical direction beside the photoconductor drum and adapted to guide fed paper to the paper stack space portion.
Preferably, the photoconductor drum comprises an a-Si-based photoconductor drum, and a peripheral speed of the cleaning roller is greater than a peripheral speed of the photoconductor drum.
Preferably, the toner comprises a magnetic toner.